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Update 用好Java中的枚举真的没有那么简单.md

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`‎docs/java/basis/用好Java中的枚举真的没有那么简单.md‎`

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Original file line number	Diff line number	Diff line change
`@@ -65,15 +65,16 @@ public class Pizza {`
`65`	`65`	首先,让我们看一下以下代码段中的运行时安全性,其中 `==` 运算符用于比较状态,并且如果两个值均为null 都不会引发 NullPointerException。相反,如果使用equals方法,将抛出 NullPointerException:
`66`	`66`
`67`	`67`	```java
`68`		`-if(testPz.getStatus().equals(Pizza.PizzaStatus.DELIVERED));`
`69`		`-if(testPz.getStatus() == Pizza.PizzaStatus.DELIVERED);`
	`68`	`+Pizza.PizzaStatus pizza = null;`
	`69`	`+System.out.println(pizza.equals(Pizza.PizzaStatus.DELIVERED));//空指针异常`
	`70`	`+System.out.println(pizza == Pizza.PizzaStatus.DELIVERED);//正常运行`
`70`	`71`	```
`71`	`72`
`72`		-对于编译时安全性,我们看另一个示例,两个不同枚举类型进行比较,使用equal方法比较结果确定为true,因为`getStatus`方法的枚举值与另一个类型枚举值一致,但逻辑上应该为false。这个问题可以使用==操作符避免。因为编译器会表示类型不兼容错误:
	`73`	`+对于编译时安全性,我们看另一个示例,两个不同枚举类型进行比较:`
`73`	`74`
`74`	`75`	```java
`75`		`-if(testPz.getStatus().equals(TestColor.GREEN));`
`76`		`-if(testPz.getStatus() == TestColor.GREEN);`
	`76`	`+if (Pizza.PizzaStatus.DELIVERED.equals(TestColor.GREEN));// 编译正常`
	`77`	`+if (Pizza.PizzaStatus.DELIVERED == TestColor.GREEN);// 编译失败,类型不匹配`
`77`	`78`	```
`78`	`79`
`79`	`80`	`## 4.在 switch 语句中使用枚举类型`

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